Siemens SIRIUS 3RT1025-1AG20 Power Contactor — Size S0, Screw Terminals
The Siemens 3RT1025-1AG20 is a SIRIUS power contactor in the compact Size S0 frame, rated for motor switching at 7.5 kW in AC-2 duty at 400 V and 15.5 A in AC-4 duty at 400 V — the AC-4 figure governs reversing or inching applications where the contactor makes and breaks the load under full current. Mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 50022; the 45 mm width and 85 mm height fit standard panel layouts, with side-by-side mounting permitted for multi-contactor assemblies. Main circuit screw terminals accept solid or stranded conductors up to 2x 10 mm² (AWG 8), while auxiliary and control circuit terminals handle up to 2x 4 mm² (AWG 12) — sized for typical motor branch circuits without needing terminal adapters.
Motor Duty Ratings & Short-Circuit Coordination
Rated at 7.5 kW AC-2 at 400 V (slip-ring motor starting) and 11 kW at 690 V; the same contactor delivers 10 kW at 500 V and 11 kW at 690 V — the higher voltage ratings let it serve 690 V industrial networks common in mining or marine installations. For AC-4 reversing duty, the 15.5 A at 400 V rating is the limiting factor — ensure the motor full-load current stays under that threshold when the contactor makes and breaks stalled-rotor current. Short-circuit coordination: Type 1 requires a 63 A gL/gG fuse; Type 2 requires 25 A gL/gG. The 25 A fuse limits let-through energy to protect the contactor during a bolted fault, keeping it operational after the event.
Environmental & Compliance
Rated for pollution degree 3 (conductive pollution typical in industrial enclosures), operating from -25 °C to +60 °C. Front face is IP20; terminal area is IP00 — install in a cabinet with at least IP2X door to meet touch-safe requirements. RoHS compliant per substance prohibitance date of 01.07.2006. Mechanical endurance is 10 million operations typical.
Auxiliary Contact Ratings
Built-in auxiliary contacts rated: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V — these cover control-circuit switching for PLC inputs, pilot lights, and interposing relays across common control voltages.